Transparency

[Brent Fraser]

Doug,

  Transparency for raster layers is defined with the
OFFSITE keyword.  The value is the color number
the image's palette.

e.g. 
LAYER
  NAME ortho
  TYPE RASTER
  STATUS DEFAULT
  DATA "83P_01s_10TM.tif"
  OFFSITE 2
END

means the third color (since there is a color index 0)
in the image's pallete for this layer is to be considered
transparent when reading the tif file and writing the
pixels into the target GIF (i.e tif pixels with color index 3
are not written into the GIF).

Funny thing is, this is from old mapserver 3.2
documentation (and email).  I couldn't find it in the 3.3
doc.

Hope this helps...

Brent Fraser

bfraser at geoanalytic.com 
GeoAnalytic Inc.
#300 , 700 - 4th Avenue SW Calgary, AB
Canada T2P 3J4
Tel:  (403)213-2700 Fax:  (403)213-2707
www.geoanalytic.com


----- Original Message ----- 
From: "Doug Nebert" <ddnebert at fgdc.gov>
To: "Mapserver Users" <mapserver-users at lists.gis.umn.edu>
Sent: Friday, July 21, 2000 1:20 PM
Subject: Transparency


> All:
> 
> I would like to manufacture certain layers as being transparent outside
> of the opaque features so they can be overlain on similar maps from 
> other servers. I want roads opaque, background transparent. 
> 
> Is there a correct way to specify the transparent color bin to use,
> through mapfile or other setting?  I am using mapserv with the old
> gd that supports GIF format. I understand that the PNG files use a
> different method for transparency, but would hope that this is 
> defined in a single way via map file. Is it defined at all?
> 
> Doug.
> 
> -- 
> Douglas D. Nebert
> Geospatial Data Clearinghouse Coordinator 
> FGDC Secretariat Phone: +1 703 648 4151 Fax: +1 703 648-5755 
> Pager Messaging: http://clearinghouse3.fgdc.gov/dougmsg.html